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Systematic characterization of DRIE-based fabrication process of silicon microneedles

: Held, J.; Gaspar, J.; Ruther, P.; Hagner, M.; Cismak, A.; Heilmann, A.; Paul, O.

LaVan, D.A. ; Materials Research Society -MRS-:
Microelectromechanical systems - materials and devices : Symposium held November 26 - 28, 2007, San Francisco, California, U.S.A.; Symposium DD, "Microelectromechanical Systems - Materials and Devices" was held ... at the 2007 MRS fall meeting
Warrendale, Pa.: MRS, 2008 (Materials Research Society Symposium Proceedings 1052)
ISBN: 978-1-558-99990-9
ISSN: 0272-9172
Symposium DD "Microelectromechanical Systems - Materials and Devices" <2007, San Francisco/Calif.>
Materials Research Society (Fall Meeting) <2007, Boston/Mass.>
Fraunhofer IWM ()

This paper reports on the systematic characterization of a deep reactive ion etching based process for the fabrication of silicon microneedles. The possibility of using such microneedles as protruding microelectrodes enabling to electroporate adherently growing cells and to record intracellular potentials motivated the systematic analysis of the influence of etching parameters on the needle shape. The microneedles are fabricated using dry etching of silicon performed in three steps. A first isotropic step defines the tip of the needle. Next, an anisotropic etch increases the height of the needle. Finally, an isotropic etch step thins the microneedles and sharpens their tip. In total, 13 process parameters characterizing this etching sequence are varied systematically. Microneedles with diameters in the sub-micron range and heights below 10 m are obtained. The resulting geometry of the fabricated microneedles is extracted from scanning electron micrographs of focused ion beam cross sections. The process analysis is based on design-of-experiment methods to find the dominant etch parameters. The dependence of the needle profiles on process settings are presented and interpolation procedures of the geometry with processing conditions are proposed and discussed.